Recommended sublimation pressure and enthalpy of benzene

Recommended vapor pressures of solid benzene (CAS Registry Number: 71-43-2) which are consistent with thermodynamically related crystalline and ideal-gas heat capacities as well as with properties of the liquid phase at the triple point temperature (vapor pressure, enthalpy of vaporization) were established. The recommended data were developed by a multi-property simultaneous correlation of vapor pressures and related thermal data. Vapor pressures measured in this work using the static method in the temperature range from 233 K to 260 K, covering pressure range from 99 Pa to 1230 Pa, were included in the simultaneous correlation. The enthalpy of sublimation was established with uncertainty significantly lower than the previously recommended values.     

Electronic structure of a metal-organic copper spin-1/2 molecule: bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II)

The metal-organic molecule bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) (Cu(CNdpm)2) (C24H36N2O4Cu, Cu(II)) is a copper spin-1/2 system with a magnetic moment of 1.05 +/- 0.04 muB/molecule, slightly smaller than the 1.215+/-0.02 muB/molecule for the larger size copper spin-1/2 system C36H48N4O4Cu.C4H8O (bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) 4,4'-bipyridylethene-THF). There is generally good agreement between photoemission from vapor-deposited thin films of the C24H36N2O4Cu on Cu(111) and Co(111) and model calculations. Although this molecule is expected to have a gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, the molecule remains surprisingly well screened in the photoemission final state.     

Crystal structure and vapor pressure of a copper(II) complex with 2,2,6,6-tetramethyl-4-fluoroheptane-3,5-dione

Synthesis and single crystal X-ray diffraction study were carried out for copper(II) 2,2,6,6-tetramethyl-4-fluoroheptane-3,5-dionate (Bruker AXS P4 automated diffractometer, MoK _α radiation). Crystal data for C₂₂H₃₆CuF₂O₄: a = 5.9165(4) Å, b = 10.2787(7) Å, c = 10.5223(8) Å, α = 81.383(3)°, β = 76.106(3)°, γ = 83.778(3)°, space group P $\bar 1$ , V = 612.42(7) ų, Z = 1, d _x = 1.264 g/cm³. The structure is molecular; the copper atom has a square plane coordination formed by the oxygen atoms of two β-diketonate ligands; the average Cu-O distance is 1.895 Å, ∠O-Cu-O 92.5°. Only van der Waals interactions are realized between the molecules in the structure. The temperature dependences of the saturated vapor pressure were studied by the mass transfer technique, and the standard thermodynamic parameters of sublimation were derived for the complex, ΔH _subl ⁰ = 115.6 ± 1.1 kJ/mol, ΔS _subl ⁰ = 204.9 ± 2.5 J/mol·K.     

Vapor pressure and enthalpy of vaporization of linear aliphatic alkanediamines

Vapor pressures and the molar enthalpies of vaporization of the linear aliphatic alkanediamines H₂N–(CH₂)_n–NH₂ with n = (3 to 12) have been determined using the transpiration method. A linear correlation of enthalpies of vaporization (at T = 298.15 K) of the alkanediamines with the number n and with the Kovat’s indices has been found, proving the internal consistency of the measured data.     

Palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate) catalyzed Suzuki, Heck, Sonogashira, and cyanation reactions

Palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate): a structurally well-defined O-containing transition metal complex is reported as an efficient catalyst for Suzuki, Heck, and Sonogashira cross-coupling reactions. The protocol was also applied successfully for cyanation of aryl halides under milder operating conditions. The system tolerated the coupling of various aryl halides with alkenes, alkynes, and organoboronic acid along with the cyanation of aryl halides providing good to excellent yields of desired products.     

Thermal investigation of bis(methoxy-β-diketonates) of copper(II) — novel CVD precursors of copper films. Crystal structure of bis(2,2,6,8-tetramethyl-6-methoxynonan-3,5-dionato)copper(II)

Seven copper(II) bis-chelates derived from novel sterically hindered ligands — methoxy-β-diketones     

N-Arylation of aliphatic, aromatic and heteroaromatic amines catalyzed by copper bis(2,2,6,6-tetramethyl-3,5-heptanedionate)

Copper bis(2,2,6,6-tetramethyl-3,5-heptanedionate) was found to be an efficient catalyst for N-arylation of aliphatic, aromatic and heteroaromatic amines with aryl iodides/bromides under mild conditions. The system tolerated a variety of hindered and functionalized amines/aryl halides and the desired N-aryl amines were obtained in good to excellent yields.     

Investigations into the preparation of sila-β-diketones via 2-trimethylsilyl-1,3-dithianes: structural characterization of a second polymorph of bis(2,2,6,6-tetramethyl-2-sila-3,5-heptanedionato)copper(II)

The sila-β-diketone, 2,2,6,6-tetramethyl-2-silaheptane-3,5-dione (tmshdH), was synthesized by the condensation of the anion of 2-trimethylsilyl-1,3-dithiane with 1-bromo-3,3-dimethylbutan-2-one, followed by unmasking of the latent carbonyl moiety with HgO/HgCl₂. A monoclinic polymorph of the known copper(II) complex, Cu(tmshd)₂, was crystallized and studied by X-ray diffraction methods and found to be disordered like the orthorhombic one. Attempts to synthesize the disilylated β-diketone, 2,2,6,6-tetramethyl-2,6-disilaheptane-3,5-dione and monosilylated 4,4-dimethyl-4-sila-3-oxo-pentanal using the dithiane method were not successful. However, the 1,3-dithianyl precursors, along with the impurity 2,2^′-bis(trimethylsilyl)-2,2^′-bi-1,3-dithiane, were studied crystallographically. Large stereoelectronic and steric effects on the solid-state bonding parameters were observed for these molecules.     

Temperature dependence vapour pressure measurements of Mg(tmhd)2(tmeda) [(tmhd = 2,2,6,6-tetramethyl-3,5-heptanedione, tmeda = N,N,N′,N′-tetramethylethylenediamine]

The reaction between the magnesium β-diketonate complex Mg(tmhd)₂(H₂O)₂ and 1 equiv. of N,N,N′,N′-tetramethylethylenediamine (tmeda = Me₂NCH₂CH₂NMe₂) in hexane at room temperature yielded Mg(tmhd)₂(tmeda). The standard enthalpy of sublimation (83.2 ± 2.3 kJ mol⁻¹) and entropy of sublimation (263 ± 6.3 J mol⁻¹ K⁻¹) of Mg(tmhd)₂(tmeda) were obtained from the temperature dependence vapour pressure, determined by adopting a horizontal dual arm single furnace thermogravimetric analyser as a transpiration apparatus. From the observed melting point depression DTA, the standard enthalpy of fusion (58.3 ± 5.2 kJ mol⁻¹) was evaluated, using the ideal eutectic behaviour of Mg(tmhd)₂(tmeda) as a solvent with bis(2,4-pentanedionato)magnesium(II), Mg(acac)₂ as a non-volatile solute.     

Palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate): an efficient catalyst for regioselective C-2 arylation of heterocycles

Palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate), a structurally well defined O-containing transition metal complex is reported as an efficient catalyst for regioselective direct C-2 arylation of heterocycles with aryl halides. The present protocol is applicable to a wide variety of heterocycles providing good to excellent yields of products.     

Crystal and molecular structures of bis(2,2,6,6-tetramethyl-3-methylaminoheptan-5-onate) copper(II) and nickel(II)

Two bis-chelates M(tmih)₂ (M = Cu(II), Ni(II), tmih = (CH₃)₃C(NCH₃)CHCOC(CH₃)₃)^? are synthesized and their crystal structures are determined using XRD (Bruker APEX-II diffractometer with a CCD detector, λMoK _α, λCuK _α, graphite monochromator, T = 240(2) K and 296(2) K): Cu(tmih)₂ (I) (space group P2₁/c, a = 12.9670(8) Å, b = 18.4921(9) Å, c = 11.0422(6) Å, β = 93.408(4)°, V = 2643.1(3) ų, Z = 4) and Ni(tmih)₂ (II) (space group P2₁/c, a = 12.810(2) Å, b = 18.529(2) Å, c = 11.243(2) Å, β = 91.959(7)°, V = 2667.1(6) ų, Z = 4). The complexes are isostructural; the coordination polyhedron of metal atoms is a flattened tetrahedron formed from two O atoms (Cu-O of 1.901(2) Å, 1.892(2) Å, Ni-O of 1.845(2) Å, 1.833(2) Å) and two N atoms (Cu-N of 1.976(3) Å, 1.972(3) Å, Ni-N of 1.911(2) Å, 1.920(2) Å) of the ligand; the chelate OMN angles (M = Cu(II), Ni(II)) are in the 87.4–93.1° range; the OMO and NMN angles are 162.2° and 167.2° in I, 171.1° and 173.2° in II. The complexes have the molecular structures formed from isolated molecules bonded by van der Waals interactions. Using a quantum chemical hybrid M06 method, the structures of copper(II) chelates with the H, CH₃, CH₂CH₃, CH(CH₃)₂, and C(CH₃)₃ substituents at the nitrogen atom are calculated. Found that with a bulky substituent at the nitrogen atom, the formation of chelates is hindered due to the intraligand repulsion between the atoms of this substituent and the tert-butyl group.     

Synthesis and structure of trans-diaquabis(dimethylsulfoxide)bis(3,5-dinitrobenzoato)copper(II)

Single crystal of [Cu(DMSO)₂(3,5-DNB)₂(OH₂)₂], where DMSO-dimethylsulfoxide, 3,5-DNB-3,5-dinitrobenzoate, has been synthesized and its crystal structure is determined. Crystals belong to monoclinic symmetry, space group is P2₁/n, Z = 2, a = 10.911(4) Å, b = 5.362(2) Å, c = 22.673(7) Å, β = 92.06(2)°, V = 1325.8(1) ų, T = 293 K. Final value of R = 0.040 was obtained for 1804 independent reflections with I > 3σ(I). The structure is built from complex molecules.     

Thermal behavior of copper(II) 4-nitroimidazolate

The thermal behavior of copper(II) 4-nitroimidazolate (CuNI) under static and dynamic states are studied by means of high-pressure DSC (PDSC) and TG with the different heating rates and the combination technique of in situ thermolysis cell with rapid-scan Fourier transform infrared spectroscopy (thermolysis/RSFTIR). The results show that the apparent activation energy and pre-exponential factor of the major exothermic decomposition reaction of CuNI obtained by Kissinger’s method are 233.2 kJ mol⁻¹ and 10^17.95 s⁻¹, respectively. The critical temperature of the thermal explosion and the adiabatic time-to-explosion of CuNI are 601.97 K and 4.4∼4.6 s, respectively. The decomposition of CuNI begins with the split of the C-NO₂ and C-H bonds, and the decomposition process of CuNI under dynamic states occurs less readily than those under static states because the dynamic nitrogen removes the strong oxidative decomposition product (NO₂). The above-mentioned information on thermal behavior is quite useful for analyzing and evaluating the stability and thermal charge rule of CuNI.     

Thermal decomposition kinetics and mechanism of Cu(II), Zn(II) and Cd(II) complexes derived from fluorenone anthranilic acid

Copper(II), zinc(II) and cadmium(II) complexes of the Schiff base, fluorenone anthranilic acid were prepared and characterized by elemental analysis, magnetic measurements, conductivity experiments and electronic and infrared spectral studies. The thermal decomposition kinetics and mechanism of these chelates was studied from TG data.     

Study of kinetics and mechanism of the acid dissociation of copper(II) complex of novel C-functionalized macrocyclic dioxotetraamines

The kinetics of the acid dissociation of copper(II) complexes of novel C-functionalized macrocyclic dioxotetraamines has been studied by means of a stopped-flow spectrophotometer. The acid dissociation rate follows the law V_d = C_comkK₁K₂H ²/(1+K₁H+K₁K₂H ²). From the experimental facts we have obtained, the dissociation kinetics are interpreted by a mechanism involving the negatively charged carbonyl oxygen of the complex being rapidly protonated in a pre-equilibrium step, the rate-determining step being intramolecular hydrogen (enolic tautomer) migration (to imine nitrogen). The dissociation rate reached a plateau in the strongly acidic solution. By means of temperature coefficient method, ΔH ^φ, ΔS ^φ of the pre-equilibrium step and ΔH ^≠, ΔS^≠ of the rate-determining step were obtained. The results of 13-membered macrocyclic dioxotetraamines have been discussed. The influence of the substituents to the acid dissociation rates has also been discussed. The Bronsted type linear free energy relationships do also exist in these C-functionalized dioxotetraamine copper(II) complexes.     

Synthesis,X-ray diffraction study,and crystal structure analysis of novel copper Alkoxy-β-diketonates: bis(6,2-dimethyl-6-methoxy-3,5-heptanedionato) copper(II) and bis(1-phenyl-4-methyl-4-methoxy-1,3-pentanedionato) copper(II)

This article is a continuation of the structural study of Cu(II) complexes with alkoxy-β-diketones [1]. Alkoxy-β-diketones, possessing the same complexing ability as classical β-diketones, are more accessible and inexpensive ligands. In some properties (e.g., volatility), metal complexes with these ligands are closely related to metal β-diketonates and can effectively replace them in some important coating methods, including the MOCVD method. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 6, pp. 169–175, November–December, 1994. Translated by T. Yudanova     

Saturated Vapor Pressure and Crystal Structure of Bis-(2-imino-4-pentanonato)copper(II)

A comprehensive study of copper(II) bis-ketoiminate including tensimetric analysis of sublimation and structure solution has been carried out. The temperature dependence of saturated vapor pressure over Cu(ki)₂ crystals derived by the flow method is expressed by the equation lnP_(atm)} = 25.31-13750/T, H _subl = -114.2 ± 1.3 kJ· mole^-1, S_subl =210.2 ± 3.0> J· mole^-1 · K^-1. Crystal data for CuO₂N₂C₁₀H₁₆: a=15.143(3), b=16.681(8), c=13.795(32) , space group Ccca, Z=12, d _calc = 1.47 g/cm³, R=0.029. The structure is molecular and consists of crystallographically independent Cu(ki)₂ complexes of two types, one with a cis structure and the other with a cis–trans disordering. The copper atom has a plane square environment of two oxygen and two nitrogen atoms. In the cis isomer, Cu–O 1.938 and Cu–N 1.895 ; in the disordered complex, all four Cu–O(N) distances are 1.901 .     

Synthesis of Benzimidazoles and Benzoxazoles Using Palladium Bis(2,2,6,6-tetramethyl-3,5-heptanedionate) as a Novel Catalyst

Structurally well-defined palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate) complex is reported to be an efficient catalyst for the synthesis of benzimidazole and benzoxazole derivatives in good yields. A novel approach for one-pot synthesis of benzimidazoles via direct reductive amination and N-arylation followed by hydrogenation–cyclization methodology is also described.     

Synthesis,characterization, crystal structure and non-isothermal dehydration kinetics of a copper(II) complex

A three-dimensional complex, [CuL₂(H₂O)]₂ (HL?=?3-hydroxy-1-adamantanecarboxylic acid), C₄₄H₆₄Cu₂O₁₄, was synthesized under hydrothermal conditions from CuCO₃?·?Cu(OH)₂ and HL. The crystal structure of the complex was determined by X-ray crystallography and its thermal behavior and IR spectra examined. The non-isothermal dehydration kinetics of the complex were investigated using the Achar differential method.